Introduction

The file system events API provides a way for your application to ask for notification when the contents of a directory hierarchy are modified. For example, your application can use this to quickly detect when the user modifies a file within a project bundle using another application.

It also provides a lightweight way to determine whether the contents of a directory hierarchy have changed since your application last examined them. For example, a backup application can use this to determine what files have changed since a given time stamp or a given event ID.

You should read this document if your application works with a large number of files—particularly if your application works with large hierarchies of files.

Organization of This Document

This document is organized into the following chapters:

• Technology Overview—describes the file system events API and explains how it works at a high level.

• Using the File System Events API—explains how to use the file system events API, from creating an event stream to writing a handler, including code examples to help you quickly get started.

• File System Event Security—describes the security features of the file system events API.

• Kernel Queues: An Alternative to File System Events—explains the kernel queues mechanism, describes when it may be appropriate to use the kernel queues API in lieu of the file system events API, and includes a brief code example to show you how to use it.